There basically only a handful of cards answering that and a few game items mentioning it. Don't overthink it is my first word of advice. You'll wanna look up that reddit post that explains it, I don't have the link or the time to do so for you, but the author spends some serious time and effort connecting dots and makes a very compelling argument for what happened between the 3 'guardians'. And for heaven's sake, the name of his handcannon was NOT rose!!! The weapon was symbolically called a rose in the card, but was not named rose! And on that topic, that's The Last Word! [spoiler]please look up the reddit post, cuz what I just said will totally crack you up when you read it xD[/spoiler]